She surged past some of New Zealand's best-known distance runners and previous New Zealand 1500m record holders in Anne Audain, Dianne Rodger, Anne Hare, Lorraine Moller, Christine Pfitzinger and Toni Hodgkinson.
What is astonishing is Van Dalen' progress in a week.
Last week the former Wanganui Collegiate athlete who is currently based at Stony Brook University in New York, had a personal best of 4min 11.59sec for the distance and was, at best, a long shot to make the Olympic team.
She needed to run 4min 7sec, or the IAAF A standard of 4min 6sec if Hamblin was running, to come into Olympics contention. Hamblin's withdrawal meant Van Dalen needed to reach the slower of the two times to be nominated by Athletics New Zealand.
Last Saturday in New Jersey, Van Dalen took 3.5sec off her previous best in running 4min 8.10sec. Yesterday she sliced another 2.3sec off that and put her within touching distance of Hamblin's New Zealand record of 4min 4.82sec, set in Spain last July.
The 23-year-old still needs to be nominated by Athletics New Zealand and ratified by the New Zealand Olympic Committee.
Interestingly enough her New Zealand coach Alec McNab is just a month away from completing his term as Athletics New Zealand president.
Twin sister Holly, at home in Wanganui recovering from knee surgery, and mother Susie were swamped with phone calls yesterday. Holly soon tracked down a video of Lucy's race.
Mother Susie, in fact, returned from a visit to London just last Saturday and clearly has to consider the prospect of another visit very soon, if Lucy makes the Games team.
Holly noted that the unfortunate Nicky Hamblin had emailed Lucy Van Dalen earlier this week and offered her moral support in trying to break the Games mark.
"It's an A standard, you can't do any better than that!"
Van Dalen completed her NCAA track season a couple of weeks ago and planned to spend the next month trying to qualify for London.
"She was feeling fresh and ready to go," said Holly. "Now (if selected) she can train now and just turn up for the Olympics."
The two sisters have conversed in several phone calls since the San Diego race.